Production of negative for offset printing plates



Dec. 19, 1933. J. WILLIAMS 1,939,749

PRODUCTION OF NEGATIVE FOR OFFSET PRINTING PLATES Filed March 51, 1952 J9 5 19 $95 7 1 9 W 777% 7 J6 fZUWZZZfi kTO/WY wf/z'czfizs,

Patented Dec. 19, 1933 PATENT OFFICE PRODUCTION OF NEGATIVE FOR OFFSET PRINTING PLATES John Williams, Chicago, 111.

Application March 31, 1932. Serial No. 602,147

7 Claims.

This invention relates to improvements in method of producing a negative for printing plates and by means of the use of which method it will be possible to convert a fiat bed printing plate (i. e. a half tone copper plate) into an offset printing plate.

To the attainment of these ends and the accomplishment of other new and useful objects as will appear, the invention consists in substantially the steps in the method hereinafter more fully described and claimed, taken in connection with the accompanying drawing, showing a manner in which the invention may be carried into operation, and in which drawing Figure 1 is a plan view of an etched copper plate.

Figure 2 is a plan view of a die plate produced from the copper plate and reverse to the copper plate.

Figure 3 is a plan view of a transparent mold plate which is a negative taken from and reverse to the die plate, but a positive with respect to the original copper plate.

Figure 4 is a sectional view taken on line 4-4, 25 Figure 3, of the negative plate covered with a filling material.

Figure -5 is a view similar to Figure 4, showing the filling material removed from the high portions and filling the low portions of the negative plate.

Referring more particularly to the accompanying drawing the numeral designates generally a copper plate which is etched in the usual manner to produce high portions 11 and low portions 12.

The numeral 13 designates a plate of any suitable hard non-metallic material, such for instance as a phenolic condensation product commercially known as Bakelite, or the like, up- 4 on which an impression is madefrom the plate 10, preferably, by means of a suitable hydraulic press, or in any other suitable manner to produce an impression which is reverse to the plate 10 and with the portions 14 constituting the low portions and the portion 15 the high portion of the surface of the plate, thereby forming of the plate a die.

From the die plate 15 an impression is made upon a suitable non-metallic transparent plate 18, such for example as celluloid, or the like, resulting in the production of the high portions 17 and the low portions 18, and with the further result that a negative of the plate 13 will be produced upon the plate 16 which is a counterpart or positive of the plate 10, with the portion 17 constituting the high portions and the part 18 constituting the low portion or area, identical with the corresponding parts on the originally etched copper plate 10.

This plate 16 will constitute a negative, which 0 in realityis a transparent positive of the plate 10, and from which negative the printing plate will be directly produced.

After the impression is made upon the plate 16 the face of the plate is covered with a filling 5 material 19, preferably in the form of a paste of any suitable material and consistency to fill the low portions or areas and possibly some of the portions of the surfaces of the high portions, and the filling material is allowed to dry, preferably without the application of heat, although if desired heat may be applied to expedite the drying process. The paste may be, for example, formed from oil, magnesia and lamp black, and of a plastic or semi-plastic con- 7 sistency.

After the filling material is thoroughly dry, the surface of the high portions are then cleaned in any suitable manner to remove any of the filling material or coating that may be deposited there- 30 upon, such asby means of an abrading stone or the like, with the result that the high portions of the plate will be transparent while the remaining or low portions of the plate which are covered with the filling material will be rendered opaque. 35

The final partially transparent and partially opaque plate thus produced is then used as a negative from which the subject matter delineated or depicted by the high and transparent portions of the plate or negative will be .printed upon the printing surface or plate.

The printing surface or plate is first sensitized in any suitable manner, such as by the application thereto of a film or .coating of sensitive material, and when such coating is dry, the negative 5 plate is applied to the sensitized surface of the printing plate and then exposed to light rays, which latter will pass through the transparent portions of the negative to print upon the sensitized surface of the printing plate.

The printing plate or surface is then treated and finished in the ordinary and usual manner.

While the preferred steps in the method have been herein described and claimed, it is to be understood that various changes in the method and in the steps of performing the same, within the scope of the claims, may be made, without departing from the spirit of this invention.

What is claimed as new is;-

1. The method of producing a negative for use in the production of offset printing plates, which consists in producing an etched plate of the matter to be printed, then producing by impression from said plate a reverse of such matter upon a 5 hard non-metallic plate to form a die plate, then taking from said die plate, by pressure, an impression upon a transparent plate, which is a reverse of the die plate and a positive of the original etched plate, and then rendering poro tions of the negative opaque, and from which negative a print may be obtained upon the printing surface or plate.

2. The method of producing a negative for use in the production of offset printing plates, which 5 consists in producing by impression from an original relief plate a reverse of the matter thereupon, upon a hard non-metallic plate to form a die plate, then taking from said die plate, by pressure, an impression upon a transparent plate, which is a reverse of the die plate and a positive of the original etched plate and having high and low areas, then filling the low areas with a filling material to render portions of the negative opaque, and then removing any of the g5 filling material which may be deposited upon the high areas and from which negative a print may be obtained upon the printing surface.

3. The method of producing a negative for use in the production of offset printing plates, which 0 consists in producing by impression from an original relief plate a reverse of the matter thereupon, upon a hard non-metallic plate to form a die plate, then taking from said die plate, by pressure, an impression upon a transparent plate,'

a which is a reverse of the die plate and a positive of the original etched plate and having high and low areas, then filling the low areas with a filling material to render portions of the negative opaque, and then removing by an abrading oper- 4o ation any of the filling material which may be deposited upon the high areas and from which negative a print may be obtained upon the printing surface.

4. The method of producing a negative for use in the production of offset printing plates, which consists in producing by impression from an original relief plate a reverse of the matter thereupon, upon a hardnon-metallic plate to form a die plate, then taking from said die plate, by pressure, an impression upon a transparent plate, which is a reverse of the die plate and a positive of the original etched plate and having high and low areas, then filling the low areas with a filling material to render portions of the negative opaque, then allowing said filling material to dry, and then removing any of the filling material which may be deposited upon the high areas and from which negative a print may be obtained upon the printing surface.

5. In the method of producing a negative for use in the production of offset printing plates the steps which consists in providing an etched plate of the matter to be printed, then producing a negative die plate from the etched plate, then producing by pressure a transparent plate which is a negative of the die plate and a positive of the original etched plate, and then filling the low areas of the transparent plate with an opaque material, to produce the final negative from which the final printing plate is produced.

6. In the method of producing a negative for use in the production of offset printing plates the steps which consists in providing an etched plate of the matter to be printed, then producing a negative die plate from the etched plate, then producing by pressure a transparent plate which is a negative of the die plate and a positive of the original etched plate, and then rendering a portion of the transparent plate opaque to produce the negative from which the final printing plate is produced.

7. In the method of producing a negative for use in the production of offset printing plates the steps which consist in providing an etched plate of the matter to be printed, then producing a negative die plate from the etched plate, then producing by pressure a transparent plate which is a negative of the die plate and a positive of the original etched plate, and then rendering a portion of the transparent plate opaque by the application thereto of a coating material over the desired portions of the same to produce the negative from which the final printing plate is produced.

JOHN WILLIAMS. 

